1. Field of the Invention
The present invention relates to a semiconductor device and a testing method thereof, and more particularly, it relates to a semiconductor device having a number of external terminals (output terminals) and a testing method for testing output voltage thereof.
2. Description of the Related Art
A semiconductor device provided with a driver circuit of a liquid crystal display (also referred to as a liquid crystal driver circuit, or LCD driver) drives the liquid crystal display (liquid crystal panel) by outputting multi-stage (multiple gray-scale) voltage from a number of external terminals (output pins).
Conventionally, a gray-scale voltage test of a semiconductor device provided with a liquid crystal driver circuit has been done by measuring voltage (e.g., analog voltage measurement) with using a tester. In the present specification, such a tester will be referred to as an Automatic Test Equipment by its abbreviation “ATE”, hereinafter. However, the tester should not be limited to the ATE.
However, with the increase of the number of output terminals in the semiconductor device resulting from the higher definition of the liquid crystal display and with the introduction of higher gray scale in the liquid crystal display in recent years, problems such as extended time required for a gray-scale voltage test and increased cost for testing or manufacturing the semiconductor device (liquid crystal driver circuit) have occurred.
As a method for reducing the time required for the gray-scale voltage test, Japanese Patent Application Laid-Open No. 2002-156412 describes the technique in which differential voltage between output terminal voltage of the liquid crystal driver circuit and reference voltage of an ATE (tester) is detected and then the variances of the gray-scale voltage among the terminals are tested in respective output terminals of the liquid crystal driver circuit.